PASTEURELLA HAEMOLYTICA SUBUNIT VACCINE CONTAINING CAPSULAR POLYSACCHARIDE AND MURAMYL DIPEPTIDE

Abstract: Protection of ruminants against bacterial pneumonia caused by Pasteurella haemolytica has been achieved with a subunit vaccine. The vaccine contains two principle components: capsular polysaccharide of P. haemolytica and a synthetic adjuvant, muramyl dipeptide. This vaccine prevented bacterial infection of the lungs of vaccinated animals upon challenge with P. haemolytica. In contrast, animals that were not vaccinated or animals that were vaccinated with only capsular polysaccharide alone had severe lesions and high concentrations of P. haemolytica in the lungs.

Description: PASTEURELLA HAEMOLYTICA SUBUNIT VACCINE CONTAINING CAPSULAR POLYSACCHARIDE AND MURAMYL DIPEPTIDE BACKGROUND OF THE INVENTION Field of the Invention This invention relates to protection of ruminants from the effects of stress, particularly those involving an outbreak of virulence of Paεteurella haemolytica . Pasteurella haemolytica is a gram-negative bacterium that inhabits the upper respiratory tract of ruminants. During periods of stress, the organism enters into a virulent stage and proliferates in the respiratory tract. There, it may be inhaled into the lungs, inducing a disease called pneumonic pasteurellosis or shipping fever of cattle. All U.S. cattle, sheep, and goats are susceptible. There are 16 serotypes of P. haemolytica based on chemical differences in the outer capsular polysaccharide. P. haemolytica serotype Al is the primary cause of pneumonic pasteurellosis in cattle. The resulting pneumonia is costly to the producer and difficult to treat. Some animals die. In cattle alone, shipping fever accounts for an estimated loss of three billion dollars worldwide of which $500 million dollars is from the United States. Description of Prior Art Many veterinary products are available that contain P. haemolytica but their effectiveness in preventing pneumonic pasteurellosis is questionable. Resistance to experimentally induced pneumonic pasteurellosis can be enhanced by vaccination with live P. haemolytica , but not with formalin-killed P. haemolytica , P. haemolytica leukotoxin or P. haemolytica lipopolysaccharide. In fact, it is not uncommon for some animals vaccinated with live vaccines to have complications or animals with formalin-killed vaccines to have more severe lesions than nonvaccinated animals. This applies also to the poorly immunogenic capsular polysaccharide of P. haemolytica serotype Al which is composed of N-acetylaminomannuronic acid and N-acetylmannosamine. SUMMARY OF THE INVENTION We have unexpectedly found that by addition of a muramyl peptide, the capsular polysaccharide of P. haemolytica , particularly that of type Al, can be transformed into an effective vaccine capable of providing a protection against stress-induced virulence of P. haemolytica , and is also believed to elicit bactericidal antibodies against the bacterium. In laboratory tria l s, vaccines comprising the capsular polysaccharide and adjuvant prevented bacterial infection of the lungs of vaccinated sheep upon challenge with P. haemolytica . In contrast, sheep that were not vaccinated or sheep that were vaccinated with only capsular polysaccharide had severe lesions and high concentrations of P. haemolytica in the lung. In accordance with this finding, it is an object of the invention to prepare a P. haemolytica subunit vaccine which is capable of inducing protection; in other words, a high degree of immunity against stress-induced virulence of P. haemolytica . It is also an object of the invention to prepare a P. haemolytica subunit vaccine which is safe to handle, incapable of inducing adverse side effects during vaccination, and incapable of inducing the disease in the vaccinated animal. Another object of the invention is to prepare a P. haemolytica subunit which is relatively simple, chemically defined in its constituents, and economically feasible to produce. Other objects and advantages of the invention will become readily apparent from the ensuing description. Deposit of Biological Material The P. haemolytica strain P-1075 used herein as a source of capsular polysaccharide was deposited on May 4, 1993, under the conditions of the Budapest Treaty with the American Type Culture Collection, Rockville, MD, and has been assigned Accession Number ATCC 55423. DESCRIPTION OF THE INVENTION The term "ruminant" is used throughout the disclosure to include cattle, sheep, goats, and any other cud-chewing animal, wild or domestic, which is susceptible to pneumonic pasteurellosis caused by P. haemolytica under stress conditions. Unless otherwise specified, the term Pasteurella haemolytica includes all immunogenic types, serologic types, and all strains thereof that may induce disease that is clinically similar to pneumonia caused by what is known as type Al. "Subunit vaccine" is used throughout the disclosure to mean a type of vaccine comprising distinct chemically defined components (i.e., protective antigens) which are capable, when associated with a muramylpeptide, of inducing protective immunity against stress- induced virulence of P. haemolytica . "Capsular polysaccharide" is used throughout the disclosure to mean a purified bacterial component from P. haemolytica comprised of N-acetylaminomannuronic acid and N-acetylmannosamine. Adlam et al. fProtein-Carbohydrate Interactions in Biological Systems t pp 391-393 (1986)] reports that the actual structure of the P. haemolytica Al capsular polysaccharide is →3)-β-N- acetylaminomannuronic-(l→4)-β-W-acetymannosamine-(l→ with the 4 position of the uronic acid being O-acetylated. The P. haemolytica capsular polysaccharide for use herein is recovered from the whole organism by any known method, such as the isolation and purification procedure of Adlam et al. [Journal of General Microbiology 130: 2415-2426 (1984)] described in Example 1. "Synthetic adjuvant" is used throughout the disclosure in its usual sense to mean a laboratory-synthesized substance that, when added to an antigen, causes the elicitation in vivo of an immunogenic response superior to that imparted by the antigen itself. The synthetic adjuvants contemplated for use in the invention include any of a variety of muramyl dipeptide analogs represented by the general formula: Where R is a hydrogen or a methyl group. X is an amino acid and preferentially L-Ala, L-Leu, L-ILeu, L-Val, L-Ser, L-Thr, L-(N-Methyl) Ala, D-Ala. Rl is OH , NH 2 or 0C n H 2n+1 with n being 1 , 2 , 3 or 4 R2 is OH, NH 2 , OC n H 2n+1 (with n being up to 20), sn glyceryl dipalmitoyl or Y-Z, where Y is an amino acid, preferentially L-Ala or L-Lys, and Z is OH, NH 2 , 0C n H 2n+1 with n being up to 20 or sn glyceryl dipalmitoyl. A preferred mura yl dipeptide is the N-acetylmuramyl-L- alanyl-D-isoglutamine or its glyceryl dipalmitoyl derivative (N- acetyl-muramyl-L-alanyl-D-isoglutamine, beta, gamma-dipalmitoyl-sn- glycerol) described in the examples below. Other muramyl dipeptides having the aforementioned properties and contemplated for use herein include the compounds described in the following patents: French patents BF 7422909 issued 7/30/79 and BF 7529624 issued 9/3/79; U.S. patents 4186194 issued 1/29/80 and 4235771 issued 11/25/80; and Canadian patents 1060795 issued 8/20/79 and 1060796 issued 8/21/79, herein incorporated by reference. More precisely, those compounds include Nac-Mur-L-Ala-D-Glu and Nac-Mur- L-Ala-D-isoGln-L-Lys. Also part of the invention are the mono-and diesters of Nac-Mur-L-Ala-D-Glu and the esters of Nac-Mur-L-Ala-D- isoGln. Anotherpreferredmuramyl peptide is Nac-Mur-L-Ala-D-isoGln-sn- glycerol-dipalmitoyl and the compounds described in French patent 8407340 issued 02/08/88 and its extensions, particularly U.S. 4939122 issued 7/3/90, herein incorporated by reference. Other muramyl peptides to be part of the invention are Nac-Mur- L-Ala-D-isoGln-L-Ala-2 (1' ,2' dipalmitoyl)-snglycero-3' phosphoryl ethyl amide (MTP-Pe), Nac-glucosaminyl-Nac-Mur-L-Ala-D-isoGln-L- Ala-glyceryl-dipalmitate (DTP-GDP) Nac-Mur-L-Thr-D-isoGln, Nac-Mur- L-Thr-D-isoGln-1,2 dipalmitoyl-sn-glycerol, Nac-Mur-D-Ala-D-isoGln- 1,2 dipalmitoyl-sn-glycerol, Nac-Mur-L-Ala-D-Gln and its esters. The polysaccharide and the muramyl dipeptide are conveniently maintained as separate stock solutions, wherein the agents are suspended in a suitable buffer, such as saline, phosphate buffered saline, Tris-buffered saline, or the like. When formulated into the vaccine, the stock solutions are combined with a pharmaceutically acceptable carrier or vehicle, usually mineral oil or some other oleaginous material. For stabilizing oil-based suspensions, preferred emulsifying agents are monooleates, such as sorbitan monooleate, mannide monooleates, and monooleate emulsifiers sold under the tradenames "Arlacel A" and "Montanide". In selecting an amount of muramyl dipeptide to include in the vaccine, it is important that the level is high enough to produce the desired adjuvant effect, but not so high to have an immunosuppressive effect on the vaccinated animal. The level will of course vary with the type of ruminant being treated and the regimen of administration. A person of ordinary skill in the art would be able to determine the optimum level. The relative amounts of the remaining components are not particularly critical provided that the formulation is stable and contains the desired dose level of vaccine. For the mere purpose of illustration, these relative amounts may be in a weight ratio of the muramylpeptide to the capsular polysaccharide of from about 5:1 to about 1:200, and preferably in the range of about 1:1 to about 1:20. It must of course be understood that such ratios may vary from one muramyl¬ peptide to another, and from one polysaccharide to another. In a preferred formulation protocol, stock solutions of each of the capsular polysaccharide, muramyl dipeptide, and emulsifying agent are added to the mineral oil and simultaneously emulsified. For small amounts of vaccine (i.e., < 50 doses), emulsification can be achieved. Typically, each dose of vaccine will comprise from about 10 to about 1000 μg, and preferably 50-500 μg muramyl dipeptide; and from about 10 to about 3000 μg, and preferably 500-2000 μg capsular polysaccharide. In a preferred regimen, animals are immunized by injection of 2 doses of the vaccine approximately 4 weeks apart. A maintenance dose is then administered on a yearly basis. As shown from the laboratory trials in the Examples below, the vaccine has been demonstrated to be effective in preventing bacterial infection of the lungs of vaccinated sheep upon challenge with P. haemolytica . It is also envisioned that other protective agents may be administered in combination or in conjunction with the composition of this invention. Particularly preferred agents for further broadening the protective nature of this vaccine include but are not limited to Pasteurella haemolytica leukotoxin, described by Conlon et al . (1991, Infect. I mun., 59:587-591), the contents of which are incorporated by reference herein. It has also been demonstrated that high levels of protective antibodies endowed with bactericidal activity are obtained within the first week after the first immunization and remain at high levels for more than one month. Thus, animals are protected precisely when they need it most. The invention also relates to a diagnostic assay to demonstrate, within a few days after the first injection, that animals have been immunized. The presence of antibodies specific to the P. haemolytica capsular polysaccharide which have been elicited in response to the administration of the subject vaccine may be detected using conventional immunoassays techniques. Briefly, serum of an animal or ruminant to be tested is collected and contacted with the capsular polysaccharide for a sufficient time and under conditions effective to allow specific antibody/antigen binding. Capsular polysaccharide/antibody complexes may then be detected using standard techniques. Without being limited thereto, suitable immunoassay techniques for use herein include enzyme-linked immunosorbent assays (ELISA), immunofluorescence assays (IFA), radioimmunoassays (RIA) , immunoelectrophoresis, and western blot analysis, such as described by Stites [Clinical Laboratory Methods for Detection of Antigens & Antibodies, IN: Basic & Clinical Immunology, Stites et al. (ed.), fifth edition, Lange Medical Publications, Los Altos, CA, (1984) pp. 312-352], the contents of which are incorporated by reference herein. In a preferred embodiment, antibody is detected by ELISA using capsular polysaccharide fixed on a solid substrate such as a membrane or microtiter plate. Following incubation with test serum and rinsing to remove unbound antibody, the substrate is incubated with anti-immunoglobulin tagged with an enzyme label. Enzyme activity on the solid phase is then related to the presence and/or amount of bound antibody. The practitioner skilled in the art will recognize that the reagents for the immunoassay may be incorporated into a kit. In addition, the vaccine may be included in the kit for convenience. The following examples are intended only to further illustrate the invention and are not intended to limit the scope of the invention which is defined by the claims. EXAMPLE 1 Vaccine Component Preparation Capsular polysaccharide from P. haemolytica strain P-1075 (type Al) was prepared as described by Adlam, C. , et al., Journal of General Microbiology 130:2415-2426, 1984. Essentially, the capsular polysaccharide was isolated from the supernatant of the initial bacterial cell harvest as follows. One liter of culture supernatant was placed in dialysis bags (12 - 14,500 nominal mol. wt. cutoff; Spectrum Medical Industries, Inc., Los Angeles, CA) and covered with carboxymethylcellulose (Aquacide I, Calbiochem Corp., La Jolla, CA) . The concentrated culture supernatant (about 60 ml) was mixed with 3 volumes methyl alcohol and 1% sodium acetate. The resulting precipitate was pelleted by centrifugation for 30 min at 4,080 x g (GSA rotor; Sorvall RC2-B centrifuge; DuPont, Wilmington, DE) at 4°C. The supernatant was removed, filtered in a 0.22 μm filter (Nalge Co. , Rochester, NY) and mixed with 3 volumes of acetone. The precipitate was pelleted by centrifugation for 30 min at 4,080 x g (GSA rotor; Sorvall RC2-B centrifuge; DuPont, Wilmington, DE) at 4°C. The precipitate was resuspended in water and lyophilized. The crude acetone precipitate was dissolved in 2 volumes 1/10 saturated sodium acetate and 1 volume 77% (wt/vol) phenol, shaken, and centrifuged for 1 hr at 13,500 x g (GSA rotor; Sorvall RC2-B centrifuge; DuPont, Wilmington, DE) at 4°C. The aqueous phase was removed and saved. The resultant phenol phase was similarly reextracted 3 times with 2 volumes fresh, 1/10 saturated sodium acetate. The aqueous phases were pooled and dialyzed for 2 days against 3 changes of 0.1 M CaCl 2 . The dialyzed aqueous phase was adjusted to pH 6.9. The mixture was then centrifuged at 100,000 x g (Ti50 rotor; Beckman XL-90 ultracentrifuge, Beckman Instrument Co., Palo Alto, CA) . The aqueous phase supernatant was mixed with 3 volumes ethyl alcohol with 1% sodium acetate. The precipitate was collected by centrifugation for 1 hr at 13,000 x g (GSA rotor; Sorvall RC2-B; DuPont, Wilmington, DE) at 4°C and resuspended in 10 mW Tris, 145 mW NaCl buffer, pH 7.2 containing 0.2% SDS, and 500 μg (16 U)/ml proteinase K (Amresco, Solon, OH) and heated first at 60°C for 2 hr and then overnight at 37°C. The suspension was then recycled for 1 hr over an endotoxin removing affinity column (Detoxi-gel; Pierce, Rockford, IL) . The capsular polysaccharide was precipitated from the buffer with ethyl alcohol and sodium acetate. The precipitate was resuspended in pryogen-free distilled water (Baxter Healthcare Corp., Deerfield, IL) , precipitated again with ethyl alcohol and sodium acetate, resuspended in pryogen-free distilled water and lyophilized. The capsular polysaccharide contained less than 0.25% protein [Bradford, M. M. , "A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of protein-dye binding," Analytical Biochemistry 72:248-254 (1976)] and 0.01% LPS as determined by a chromogenic limulus amebocyte lysate assay (QCL-1000, Whittaker Bioproducts, Walkersville, MD) . Muramyl dipeptide (N-acetylmuramyl-L-alanyl-D-isoglutamine) was chemically synthesized. Vaccine Formulation Separate stock solutions of capsular polysaccharide (2 mg/ml) and muramyl dipeptide (1.25 mg/ml) were prepared in 0.14 M NaCl containing 0.2% sorbitan monooleate and 0.1% formalin and chilled on ice. Vaccine 1 was formulated from 2.75 ml of capsular polysaccharide solution, 0.22 ml of muramyl dipeptide solution, 6.93 ml of a mixture of 0.2% sorbitan monooleate and 0.1% formalin, and 1.1 ml of mineral oil. Vaccine 2 was formulated from 2.75 ml of capsular polysaccharide solution and 7.10 ml of a mixture of 0.2% sorbitan monooleate and 0.1% formalin, and 1.1 ml of mineral oil. All vaccines were emulsified in the sonicator for 60 sec. Final concentrations were 0.5 mg capsular polysaccharide/ml and 25 μg muramyl dipeptide/ml of vaccine. τ.amh Field Trial Fifteen, 11-to 14-week-old (12.7 + 1.4 weeks) Columbia lambs of both sexes were used. Lambs were collected at birth, deprived of colostrum, and housed in isolation. The lambs were assigned into 3 groups. Two groups of lambs (n = 5 lambs each) were inoculated intramuscularly at days 0 and 28 with 2 ml of vaccines 1 and 2, respectively. A third group of lambs (n = 5 lambs) was not inoculated and served as challenge exposure controls. On day 42, all lambs were inoculated with tissue culture media containing bovine adenovirus strain OAV-6. The inoculum was injected intratracheally (2 ml tissue culture medium containing virus) and dispensed intranasally (1 ml tissue culture medium containing virus in each nostril). On day 46, lambs were inoculated intratracheally with 10 6 ml tryptose broth containing 4.5 X 10 6 CFU P. haemolytica/ml. On day 71, lambs were anesthetized with pentobarbital and exsanguinated. At necropsy, lesions were seen in the lungs of all lambs due to the underlying adenovirus challenge. However, lesions observed due the secondary P. haemolytica challenge varied among groups as reported in Table I, below. TABLE I Extent of Pneumonia in Lungs of Lambs after Vaccination (Average percent pulmonary consolidation) Non- Vaccine 1 Vaccine 2 Pulmonary lobe vaccinated (CP+MDP) (CP) right anterior 41 11 26 middle 40 19 33 diaphramic 2 2 1 left anterior 22 14 23 middle 41 30 50 diaphramic 7 5 7 accessory 30 10 31 Lungs were homogenized and the concentration of viable organisms was determined. The concentrations of P. haemolytica isolated from these lesions also varied among groups as shown in Table II, below. TABLE II Concentration of P. haemolytica in the Lungs After Experimental Challenge Vaccine Lesions* Isolation" Concentration 0 none B, V 5/5 2.4 x 10 7 vaccine 1 (CP+MDP) d V 0/5 0 vaccine 2 (CP) B, V 4/5 3.7 x 10 7 "Primarily bacterial (B) or viral (V) lesions. "Number positive/total number in group. "Concentration per gram of lung tissue. d CP = capsular polysaccharide and MDP = muramyl dipeptide. EXAMPLE 2 Vaccines 1 and 2 were formulated as described in Example 1. Fifteen specific pathogen-free Columbia lambs of both sexes were used in the trial. The average age of the lambs at the start of the study was 62 days (range 56-70 days) and the mean body weight was 27 kg (range 22-32 kg). The lambs were assigned into 3 vaccine groups. Groups receiving vaccines 1 and 2 (n = 5 lambs each) were inoculated intramuscularly in the right rear leg at days 0 and 28 with 2.0 ml of vaccine. A third group (n = 5 lambs) was not inoculated and served as challenge exposure controls. Vaccination sites were examined weekly and palpitated for the presence of swelling. On day 34, lambs were inoculated with tissue culture media containing bovine adenovirus strain OAV-6. The inoculum was injected intratracheally (2 ml tissue culture medium containing virus) and dispensed intranasally (1 ml tissue culture medium containing virus in each nostril). On day 38, lambs were inoculated intratracheally with 10 ml tryptose broth containing 5.7 X 10 6 CFU P. haemolytica/ml. Buprenx (0.005 mg/kg) was administered subcutaneously every 12 hours to sheep with respiratory difficulty. On day 40, lambs were anesthetized with sodium pentobarbital (1.3 gm) and exsanguinated. At necropsy, the lungs were evaluated macroscopically for bacterial and viral lesions and the vaccination site was examined for tissue damage. Pieces of the right middle lobe were taken for quantitative bacterial culture and pieces of the right middle lobe and intramuscular injection site were taken for histopathologic examination. Duplicate pieces of the right middle lobe of the lung from each lamb were diced and homogenized in 100 ml of tryptose broth. The homogenate was diluted in tryptose broth, plated on trypticase soy agar with 5% defibrinated sheep blood, and the plates were incubated for 24 hours at 37°C. Pieces of lung were fixed in 10% neutral buffered formalin solution, embedded in paraffin, sectioned, and stained with Giemsa and hematoxylin and eosin stains. Small, pea-sized nodules were felt at the vaccination site in 2/5 lambs that received vaccine 1, and in 3/5 lambs that received vaccine 2. Nodules could not be felt on any lamb by day 21. At necropsy, lesions were seen in the lungs of all lambs due to the underlying adenovirus challenge. However, lesions associated with the secondary P. haemolytica challenge varied among groups and were restricted primarily to the middle lobes of both the right and left lungs as shown in Table III, below. TABLE III Extent of Pneumonia in Lungs of Lambs after Vaccination (Average percent pulmonary consolidation) Non¬ Vaccine 1 Vaccine 2 Pulmonary lobe vaccinated (CP+MDP)* (CP) right anterior 13 14 8 middle 31 21 26 diaphramic 0 1 0 left anterior 8 4 10 middle 25 4 30 diaphramic 8 3 2 accessory 6 7 7 *CP = capsular polysaccharide and MDP = muramyl dipeptide. Overall, all lambs had histologic evidence of viral pneumonia characterized by type II pneumocyte hyperplasia and both peribronchiolar and perivascular lymphocyte cuffs. Some lambs had histologic evidence of bacterial pneumonia that varied among vaccination groups. In the nonvaccinated controls, 4/5 had evidence of bacterial pneumonia characterized by hemorrhage, fibrin, inflammatory cell infiltrates, and bacteria. In lambs vaccinated with capsular polysaccharide and muramyl dipeptide, there were minimal lesions attributed to bacterial infection. Low numbers of inflammatory cell infiltrates and small amount of hemorrhage were seen. All 5 lambs vaccinated with capsular polysaccharide had lesions characteristic of bacterial pneumonia described above. One of these lambs had lesions probably the severest of the study. The concentrations of P. haemolytica isolated from these lesions appeared to correlate with the gross and histopathologic observations as shown in Table IV, below. TABLE IV Concentration of P. haemolytica in the Lungs After Experimental Challenge Vaccine Lesions* Isolation" Range 0 Concentration 0 none B, V 4/5 2.7 X 10 x -8.4 X 10 5 2.8 X 10 5 Vaccine 1 (CP+MDP)* V 3/5 0.2-3.6 X 10 2 9.9 X 10 1 Vaccine 2 (CP) B, V 5/5 5.5 X 10°-1.7 X 10 7 3.4 x 10 6 "Primarily bacterial (B) or viral (V) lesions. "Number of lambs with P. haetπolytica/total lambs in group. "Range of concentration of P. haemolytica in the infected lungs. "Mean concentration of P. haemolytica per gram of infected lung tissue. β CP = capsular polysaccharide and MDP = muramyl dipeptide. EXAMPLE 3 The procedure of Example 2 was repeated using the same capsular polysaccharide vaccine control and nonvaccinated control groups to illustrate the efficacy of a capsular polysaccharide + muramyl dipeptide glyceryl dipalmitoyl vaccine. Capsular polysaccharide from P. haemolytica strain P-1075 (type Al) was prepared as described in Example 1. Muramyl dipeptide glyceryl dipalmitoyl is the chemically synthesized derivative of the N- acetylmuramyl-L-alanyl-D-isoglutamine of Example 1. The vaccines were formulated exactly as described in Example 1 except muramyl dipeptide glyceryl dipalmitoyl was substituted for the muramyl dipeptide. Five specific pathogen-free Columbia lambs of both sexes were selected, vaccinated, and then exposed on day 34 to ovine adenovirus strain OAV-6 and on day 38 to 5.7 X 10 6 CFU P. haemolytica/rα.1 as described in Example 2. At necropsy on day 40, the lungs were evaluated for bacterial and viral lesions and the vaccination site was examined for tissue damage and pieces were taken for histopathologic examination. Pieces of the right middle lobe were also taken for quantitative bacterial culture as described in Example 1. Small, pea sized nodules were felt at the vaccination site in 5/5 lambs that received this vaccine. Nodules could not be felt on any lamb by day 21. This lesion was characterized by multiple granulomas with lipid laden macrophages, degeneration and mineralization of myocytes, and fibrosis. At necropsy, lesions were seen in the lungs of all 5 lambs due to the underlying adenovirus challenge. However, lesions associated with the secondary P. haemolytica challenge varied among lambs and were restricted primarily to the middle lobes of both the right and left lungs as shown in Table V, below. TABLE V Extent of Pneumonia in Lungs of Lambs after Vaccination (Average percent pulmonary consolidation) Non¬ CP + MDP-GDP CP vaccinated vaccine* vaccine right anterior 13 9 8 middle 31 19 26 diaphramic 0 1 0 left anterior 8 1 10 middle 25 11 30 diaphramic 8 1 2 accessory "CP = capsular polysaccharide and MDP-GDP = muramyl dipeptide glyceryl dipalmitoyl. Overall, 1 lamb had severe areas and 2 lambs had mild areas of bacterial pneumonia characterized with pleuritis, degenerating alveolar macrophages, inflammatory cell infiltrates, fibrin and hemorrhage. The remaining 2 lambs in this group did not have evidence of bacterial pneumonia. The concentrations of P. haemolytica isolated from these lesions correlated with the gross and histopathologic observations as shown in Table VI, below TABLE VI Concentration of P. haemolytica in the lungs After Experimental Challenge Vaccine lesions" isolation" range" concentration" " none B, V 4/5 2.7 X lO^δ^ X 10 5 2.8 X 10 5 CP + MDP-GDP e vaccine V 3/5 9.2 X 10°-1.4 X 10 4 5.2 X 10 3 CP vaccine B, V 5/5 5.5 X 10°-1.7 X 10' 3.4 X 10 6 "Primarily bacterial (B) or viral (V) lesions. "Number of lambs with P. haemolytica /total lambs in group. "Range of concentration of P. haemolytica in the infected lungs. ''Mean concentration of P. haemolytica per gram of infected lung tissue. β CP = capsular polysaccharide and MDP-GDP = muramyl dipeptide glyceryl dipalmitoyl. EXAMPLE 4 Vaccine formulation Solutions of CP (5 mg ml "1 ), and MDP (5 mg ml "1 ), were prepared in Tween-saline with 0.1% formalin. For preparation of 5 ml of vaccine, 1.0 ml of CP: 0.2 or 0.5 of MDP and 2.5 to 3.3 ml of Tween-saline with 0.1% formalin were added to light mineral oil (0.5 ml) and emulsified with a sonicator for 60 seconds. Final concentrations of vaccines were 1.0 mg. CP ml "1 (CP vaccine); 1.0 mg CP ml "1 with either 0.2 or 0.5 mg MDP ml "1 (CP + MDP vaccine). Calf field trial Twelve male, Jersey calves, obtained from a local dairy, were used. The average age of calves at initial vaccination was 95 days (range 53 - 129 days). Calves were penned together outdoors during the vaccination period and moved into isolation rooms for bacterial challenge. Throughout the study all animals were housed and treated by methods approved by the American Association for Accreditation of Laboratory Animal Care. Calves were divided into 4 groups. Three calves were vaccinated with 1.0 ml CP vaccine, 3 calves were vaccinated with 1.0 ml CP + 0.2 mg MDP vaccine, and 3 calves were vaccinated with 1.0 ml CP + 0.5 mg MDP vaccine, intramuscularly on the right side of the neck at days 0 and 28. The remaining 3 calves were not vaccinated and used as challenge controls. Calves were challenged using Paεteurella haemolytica serotype Al strain L101 which is an isolate from a calf with pneumonia. Organisms for challenge of vaccinated animals and the bactericidal assay were grown in tryptose broth for 3 h at 37 β C, centrifuged at 5900 x g for 30 min at 4°C, and resuspended in tryptose broth. Cell concentrations were estimated using a spectrophotometer (80% T ; 600 nm, Coleman model 35, Bacharach Instrument Co., Pittsburgh, PA USA) and the inoculum adjusted to contain approximately 1.0 x 10 8 CFU ml "1 . Exact viable count was determined by standard plate count techniques. On day 41, Pneumonic pasteurellosis was reproduced in calves by transtracheal injection of 10 ml of 3 h tryptose broth cultures containing 2.9 x 10 8 ml CFU ml" 1 . On day 43 after vaccination, calves were anesthetized with sodium pentobarbital and exsanguinated. At necropsy, the lungs were excised and consolidated portions of each lobe were estimated. Pieces of the right middle lobe (approximately 6 to 20 gm) were taken for quantitative bacterial culture and pieces of the right middle lobe and the intramuscular injection site were taken for histopathologic examination. TABLE VII Extent of pneumonia after experimental challenge of calves immunized with vaccines containing capsular polysaccharide (CP) and muramyl dipeptide (MDP) Vaccine % total lung Bacterial Concentration consolidation Isolation CFU/g lung none 20.3 ± 10.0* A 1 b 2/3 3 . 4 X 10 8c A CP 18.1 ± 10.0 A 3/3 7 . 2 X 10 6 A CP + MDP(0.2 mg) 1.0 ± 0.5 B 0/3 0 B CP + MDP(0.5 mg) 4.2 ± 3.2 B 0/3 0 B a mean ± SE b means with same letter are not significantly different (p <0.05) c mean CFU Necropsy of calves Results given in table VII demonstrate that non-vaccinated control calves and calves vaccinated with CP had bacterial pneumonia characterized by extensive, multifocal areas of consolidation with areas of necrosis and hemorrhage in the right anterior and middle lobes, the left anterior lobe, and the accessory lobe. Fibrinous pleuritis was often seen. Lesions were accompanied by high concentrations of P. haemolytica . One calf vaccinated with CP + 0.2 mg MDP had mild, patchy consolidation in the right anterior lobe. The remaining 2 calves did not have visible lesions of bacterial pneumonia. Two calves vaccinated with CP + 0.5 mg MDP also had patchy areas of consolidation in the anterior part of both the right and left anterior lobes. The third calf did not have visible lesions. It can be also seen that Paεteurella heamolytica was not isolated from any calf in either group treated with MDP (Table VII). No gross muscle lesions were seen at the vaccine injection sites in any of the vaccinated groups. EXAMPLE 5 Vaccine formulation Solutions of CP (5 mg ml' 1 ), and MDP-GDP (5 mg ml -1 ), were prepared in Tween-saline with 0.1% formalin. For preparation of 5 ml of vaccine, 1.0 ml of CP; 1.0 ml of MDP-GDP, and 2.5 of Tween- saline with 0.1% formalin were added to light mineral oil (0.5 ml) and emulsified with a sonicator for 60 seconds. Final concentrations of vaccines were 1.0 mg CP ml "1 (CP vaccine) with 1.0 mg MDP-GDP ml -1 (CP + MDP-GDP vaccine). Calf field trial Male Jersey calves were also used in this experiment. Nine animals were assigned into 3 groups. Three calves were vaccinated with 1.0 ml CP vaccine, and 3 calves were vaccinated with 1.0 ml CP + 1.0 mg MDP-GDP vaccine intramuscularly on the right side of the neck at days 0 and 28 with 1.0 ml of vaccine. The remaining 3 calves were not vaccinated and used as challenge controls. Vaccination sites were examined and palpated weekly to determine whether swelling occurred. Animals were challenged on day 41 under similar conditions as those described previously. They were inoculated with 10 ml tryptose broth containing 2.4 x 10 8 CFU ml" 1 of P. haemolytica strain L101. It was observed that calves vaccinated with CP had extensive consolidation and high concentrations of P. haemolytica in the lesions. Calves vaccinated with CP + 1.0 mg MDP-GDP had significantly less (p < 0.5) consolidation and concentrations of P. haemolytica (Table VIII). In this group, 2 calves had small patchy areas of consolidation in both the right and left anterior lobes and the right middle lobe. The third calf did not have any visible lesions. No reactions were seen grossly or microscopically at the injection side. The results are shown in Table VIII. TABLE VII Extent of pneumonia after experimental challenge of calves immunized with vaccine containing capsular polysaccharide (CP) and MDP-sn-glyceryl-dipalmitoyl (MDP-GDP) Vaccine % total lung Bacterial Concentration consolidation Isolation CFU/gm lung none 30.6 ± 4.7* A" 3/3 2.0 x 10 8 " A CP 19.4 ± 8.3 A 3/3 1.0 x 10 8 A CP + MDP- -GDP 5.2 ± 2.7 B 1/3 7.0 X 10 3 B (1.0 mg) a mean ± SE b means with same letter are not significantly different (p <0.05) c mean CFU EXAMPLE 6 In this experiment, vaccine formulations of the invention were compared with two commercial preparations for their ability to induce at an early stage bactericidal activity in the sera of vaccinated animals. The duration of the activity was also studied. Fifteen calves were divided into 5 groups. Three calves were vaccinated with 1.0 ml CP + 0.5 mg MDP vaccine and 3 calves were vaccinated with 1.0 ml CP + 1.0 mg MDP-GDP vaccine intramuscularly on the right side of the neck at day 0. Three calves were vaccinated with Septimune PH-K (Fort Dodge Laboratories, Fort Dodge, IA) and 3 calves were vaccinated with 1-Shot (SmithKilne Beecham, West Chester, PA) as per manufacturer's recommendations. The remaining 3 calves were not vaccinated and used as controls. Sera were taken at days 0, 7, 14, 21 and 28. They were tested for their bactericidal activity as follows. Serum bactericidal activity to P. haemolytica was determined in styrene plates (Immulon 1, Dynatech Laboratories, Inc., Chantilly, VA, USA). Serum was diluted 2-fold in 0.01 M PBS, pH 7.2 with 0.5 mM CaCl 2 and 0.15 mM MgCl 2 (final volume 100 μl). 50 μl of 0.01 M PBS pH 7.2 with 0.5 mM CaCl 2 and 0.15 mM MgCl 2 containing 10% heat inactivated-fetal calf serum and 50 μl of bacterial culture (same as described for the challenging organisms) were added to each dilution and the plates were incubated at 37 β C for 120 min. After incubation, 50 μl/dilution was transferred to blood agar and the plates were incubated overnight at 37°C. The bactericidal concentration 50 was calculated as the titer of serum (diluted in buffer containing 10% fetal calf serum) required to kill 50% of organisms incubated similarly in control solutions (buffer containing 10% fetal calf serum). The following results were obtained and shown on Table IX. TABLE IX Serum killing titers of calves vaccinated with Paεteurella haemolytica p. 1075 CP+MDP, CP+ MDP-GDP and 2 commercial vaccines Day Control CP+MDP CP+MDP- ■ GDP l-shot pH-K 0 8 8 2 4 8 7 4 1028 1024 64 4 14 2 256 256 32 8 21 2 256 128 <2 8 28 8 128 128 2 16 It is clear from this table that MDP and MDP-GDP adjuvanted vaccines can induce in less than seven days high levels of bacterial antibodies which remain high over more than one month. Using the sera of these animals, it has been possible to design a diagnostic test capable of demonstrating at an early stage that animals have been immunized. This will constitute a considerable improvement since it will allow assessment before shipping that an active vaccine has been administered. The test performed in this experiment was an ELISA and specific antibodies could be detected only in vaccinated animals. It can be performed in 20 minutes for single samples and in less than 2 hours for up to several hundreds. It does not necessitate any special equipment and can be performed on the spot. Specific antibodies have also been detected using anti-bovine immunoglobulins labelled by colloidal gold. It is understood that the foregoing detailed description in the examples is given merely by way of illustration and that modification and variations may be made therein without departing from the spirit and scope of the invention.

Claims: We claim: 1. A composition comprising P. haemolytica capsular polysaccharide and muramyl dipeptide. 2. The composition of Claim 1 wherein said muramyl dipeptide is represented by the general formula: where R is a hydrogen or a methyl group; X is an amino acid and preferentially L-Ala, L-Leu, L-ILeu, L- Val, L-Ser, L-Thr, L-(N-Methyl) Ala, D-Ala; Rl is OH, NH 2 or 0C n H 2n+1 with n being 1, 2, 3 or 4; R2 is OH, NH 2 , 0C n H 2n+1 with n being up to 20, sn glyceryl dipalmitoyl or Y-Z; wherein Y is an amino acid, preferentially L- Ala or L-Lys, and Z is OH, NH 2 , 0C n H 2n+1 with n being up to 20, or sn glyceryl dipalmitoyl. 3. The composition of Claim 1 wherein said muramyl dipeptide is selected from the group consisting of N-acetylmuramyl-L-alanyl- D-isoglutamine and N-acetyl-muramyl-L-alanyl-D-isoglutamine, beta, gamma-dipalmitoyl-sn-glycerol. 4. The composition of Claim 1 wherein said capsular polysaccharide comprises N-acetylaminomannuronic acid and N-acetylmannosamine. 5. The composition of Claim 1 further comprising an oleaginous carrier and an emulsifying agent. 6. A method for protecting a ruminant animal from stress-induced virulence of Paεteurella haemolytica comprising administering to the animal a composition according to any one of claims 1-5 comprising P. haemolytica capsular polysaccharide and muramyl dipeptide. 7. The method of Claim 6 wherein said animal is a sheep. 8. The method of Claim 6 wherein said animal is a bovine. 9. A method for protecting a ruminant from stress-induced virulence of P. haemolytica comprising administering to the animal a composition comprising a protective antigen or protective antigens of P. haemolytica and muramyl dipeptide. 10. The composition of claim 1 wherein said capsular polysaccharide and muramyl dipeptide are present in an amount effective for providing protection in animals against infection by Paεteurella haemolytica. 11. The composition of claim 1 wherein said capsular polysaccharide and muramyl dipeptide are present in an amount effective for eliciting protective levels of bactericidal anti-Pasteurella haemolytica antibodies in an animal. 12. A diagnostic assay for detecting if an animal has been immunized against Paεteurella haemolytica with the composition of claim 1 comprising: a. collecting serum from said animal; b. contacting said serum with a solid substrate having said capsular polysaccharide fixed thereto; c. detecting the presence of antibody/capsular polysaccharide complex on said substrate. 13. A kit useful for protecting an animal from infection with Paεteurella haemolytica and detecting if an animal has been immunized against Paεteurella haemolytica with the composition of claim 1, comprising: a. the composition of claim 1; b. a solid substrate having said capsular polysaccharide fixed thereto; detection means effective for detecting antibodies to said capsular polysaccharide bound to said substrate.

Inventors: BROGDEN KIM A, CHEDID LOUIS, BROGDEN, KIM, A., CHEDID, LOUIS
Applicants: BROGDEN KIM A, CHEDID LOUIS, US AGRICULTURE, VACSYN SA, BROGDEN, KIM, A., CHEDID, LOUIS, THE UNITED STATES OF AMERICA, REPRESENTED BY THE S
Application year: 1994
Main classification: A61K39
IPC codes: A61K39, G01N33